Four types of trailers in common use are as follows:
1. The straight trailer is the most widely used. It has one level floor and the same dimension throughout. The straight trailer uses standard loading docks, maximum wheel size for long hauls and heavy loads with standard equipment. PA1 2. The wedge trailer is the second most popular. The floor angles down increasing the cubic feet of load space. The angle is not too steep for the standard fork lift to transverse. This trailer uses standard loading docks, loading equipment and maximum size wheels. PA1 3. The single drop trailer is the third most widely used. It has more cubic feet of load space than the straight or wedge trailer. To accomplish the drop for increased volume the trailer uses smaller wheels. The smaller wheels are not good for long distance or heavy loads. Special conveyors or ramps are needed to load from a standard dock. The split level adds to the difficulty in loading. PA1 4. The double drop trailer has received limited use except in the furniture moving industry. It is capable of having the most cubic feet of load space. In spite of its space, weight and long haul advantage its disadvantages prevent it from wide use. Its two separate floors require special conveyor systems, ramps, manual handling of freight, or special loading docks for side loading.
The use of hydraulic rams to raise a platform in a trailer is old and is shown in European Publication 153,052 of 8/24/85. The subject matter of this publication, does not, however, solve the above-named problems that are involved in double drop trailers.
It is a primary object of this invention to increase the utility of double drop trailers.